AQI health categories (US EPA scale)
The US EPA AQI scale is used by IQAir, AirNow, and most air quality monitoring services worldwide, including Pakistan's major cities. Each band has a corresponding colour code and recommended action level.
| AQI range | Category | Colour | Who is at risk? |
|---|---|---|---|
| 0–50 | Good | Green | No one |
| 51–100 | Moderate | Yellow | Unusually sensitive individuals |
| 101–150 | Unhealthy for Sensitive Groups | Orange | Sensitive groups |
| 151–200 | Unhealthy | Red | Everyone |
| 201–300 | Very Unhealthy | Purple | Everyone — serious effects |
| 301–500 | Hazardous | Maroon | Emergency conditions for all |
Source: US EPA AQI Technical Assistance Document (2018, revised 2024). PM2.5 breakpoints updated per EPA 2024 NAAQS revision.
Pakistan's smog crisis
Pakistan — and Lahore in particular — consistently ranks among the world's most polluted cities. In 2023, IQAir ranked Lahore the world's most polluted city for the second consecutive year, with an annual average PM2.5 of 97.4 µg/m³ — nearly 20 times the WHO guideline of 5 µg/m³.
Pakistan's smog season runs from October to January, driven by:
- Crop residue burning — rice stubble burning in Punjab (Pakistan and Indian Punjab) releases massive quantities of PM2.5, black carbon, and organic compounds into the atmosphere.
- Temperature inversion — cold winter nights create a dense layer of cold air near the ground that traps pollutants, preventing them from dispersing upward.
- Vehicle and industrial emissions — Lahore's rapid urban growth and high proportion of older, poorly maintained vehicles contribute significantly to PM2.5 and NO₂ levels year-round.
- Geography — the Indo-Gangetic Plain geography offers little wind to flush pollutants from the Lahore basin.
How smog harms your body
Fine particulate matter (PM2.5) is the most dangerous component of smog for human health. Because of its tiny size, it bypasses the nose and throat's natural filters and reaches the deepest parts of the lungs. From there, it can enter the bloodstream.
Short-term exposure (hours to days at high AQI) causes eye and throat irritation, coughing, shortness of breath, and worsening of asthma and COPD. Long-term exposure is associated with reduced lung development in children, chronic bronchitis, increased risk of lung cancer, cardiovascular disease, stroke, and premature death. The WHO estimates that ambient air pollution causes 4.2 million premature deaths per year globally.
Children are especially vulnerable because their lungs are still developing and they breathe more air per kilogram of body weight than adults. Studies from Lahore have found measurable reductions in lung function in children attending schools near high-traffic roads during smog season.
Protecting yourself during smog
When the AQI is above 100, a layered approach is most effective:
- Stay informed. Check IQAir or the PakAQI app before planning outdoor activities. AQI is typically worst in the early morning and evening due to temperature inversions, and better in the afternoon.
- Wear the right mask. An N95 or FFP2 respirator (with a proper seal) is effective against PM2.5. Surgical and cloth masks are not. N95s are available at most Pakistani pharmacies for Rs. 40–150 each.
- Improve indoor air. A HEPA air purifier significantly reduces indoor PM2.5. Keep windows closed during smog episodes. During cooking, use exhaust fans — indoor cooking, especially on gas stoves, adds PM2.5 to indoor air.
- Limit exertion outdoors. Exercise increases your breathing rate and depth, pulling more polluted air deep into your lungs. Shift outdoor exercise to the afternoon when AQI is lower, or move it indoors entirely on severe smog days.
- Keep medication accessible. If you have asthma or COPD, carry your reliever inhaler at all times during smog season. Speak to your doctor about a smog action plan before the season starts.
Frequently asked questions
What is AQI and how is it calculated?
AQI (Air Quality Index) is a standardised scale (0–500) that converts raw pollutant concentrations — primarily PM2.5, PM10, ozone, NO₂, SO₂, and CO — into a single number. The US EPA formula maps each pollutant concentration to a sub-index using breakpoint tables, then takes the highest sub-index as the AQI. A higher number means worse air quality.
Why is Lahore's AQI so high in winter?
Lahore's winter smog is driven by a combination of crop residue burning in Punjab (October–November), cold temperatures causing temperature inversion that traps pollutants near the ground, vehicle and industrial emissions, and construction dust. The Ravi and Chenab plains geography limits air dispersion. AQI readings of 300–500+ are common in Lahore from November to January.
What is PM2.5 and why does it matter?
PM2.5 refers to fine particulate matter 2.5 micrometres or smaller in diameter — about 30 times thinner than a human hair. These particles penetrate deep into the lungs and can enter the bloodstream, contributing to heart disease, stroke, lung cancer, and chronic respiratory disease. PM2.5 is the primary health concern in Pakistani smog episodes.
Who counts as a sensitive group?
Sensitive groups include: children (whose lungs are still developing), adults over 65, people with asthma or COPD, people with cardiovascular disease or heart failure, pregnant women, and outdoor workers with prolonged exposure. These groups experience health effects at lower AQI levels than healthy adults.
Does an N95 mask protect against smog?
A properly fitted N95 (or FFP2) respirator filters at least 95% of airborne particles including PM2.5. Surgical masks and cloth masks offer far less protection against fine particles. For effective protection, the N95 must be worn with a tight face seal — beard stubble significantly reduces effectiveness. N95s are widely available in Pakistani pharmacies.
Where can I check the live AQI in Pakistan?
The most reliable sources for Pakistan are: IQAir (iqair.com) which shows live and historical data for Lahore, Karachi, Islamabad, and other cities; the PakAQI mobile app operated by the Pakistan Metrological Department; and the US Embassy air quality monitors in Islamabad and Lahore which post hourly PM2.5 readings.
What indoor steps reduce smog exposure?
Keep windows and doors closed during high AQI periods. Use a HEPA air purifier (Lahore's winter smog makes this a worthwhile investment). Seal door and window gaps with wet towels during peak smog hours. Avoid cooking with wood or coal indoors. Run vehicle engines outside garages before entering. Run an air conditioner on recirculate mode rather than fresh air intake.
Can smog affect my eyes and skin?
Yes. PM2.5 and smog chemicals (ozone, NO₂) cause eye irritation, redness, and watering. Skin exposure to fine particles is linked to oxidative stress and may worsen conditions like eczema. Wearing wraparound glasses outdoors reduces eye exposure. Washing the face and hands after coming indoors from a high-AQI environment is recommended.